Stepping mechanism



Dec. 29, 1925. 1,567,053

l F. H. HIBBARD STEPPING MECHANISM Filed March 13, 1924 Patented Dec. 29,1925.

UNITED STATES PATEN OFFICE.

i FRANK .'E. HIBBARD, 0F ARLINGTON, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEN YORK, N. Y., A CORPORATION OF NEW YORK.

STEPPING MECHANISM.

Application mea March s, i924. seran No. 696,479.

To all whom it may concern:

Be it known that I, FRANK H. HIBBARD, a citizen of the United States of America, residing at Arlington, in the county of Hudson, State of New Jersey, have invented certain new and useful Improvements in Stepping Mechanism, of which the following is a full, clear, concise, and exact description..

`This invention relates to an actuating mechanism employinc a pawl and ratchet wheel for effecting tie step-by-step movement of a switch operating element of a selector used in automatic telephone systems, and more particularly it relates to a selfinterrupting stepping magnet for advancing a switch on the back stroke of the magnet armature.

The object is to improve the efficiency and reduce the maintenance cost of such devices.

There are a number of stepping devices known in which the work is done on the back stroke of the armature of the stepping magnet; that is to say, the magnet when energized stores up mechanical energyin .a spring which, on the opening of the circuit of the magnet, does the work of advancing the shaft while the armature is recovering its stroke. In these self-interrupting magnet structures an adjustable make and break contact device is provided to control the energization and deenergization of the magnet at the proper time. This contact device is adjusted to provide a long closure of the contacts to permit the magnet to build up `its field to the proper strength and before the end of the stroke is reached this contact must be opened to prepare for the back stroke, but at this instant the pawl has not yet reached the nextl tooth in the ratchet wheel and so the momentum of the moving parts must be used to throw the pawl the remaining distance to permit the pawl to engage said tooth. However, as soon as the magnet circuit is opened, the retracting spring associated with the armature comes into play and opposes this further throw, inasmuch as the moving parts are light and have little inertia, the margin in these devices is rather small. Conversely, since the contact closes again at the beginning of the back or driving stroke of the armature, the circuit is closed through the magnet and it begins to build up in opposition to the retractiiig spring. This means that the spring must be so constructed that it works faster than the magnet can build up its operating strength. This is particularly objectionable when the stepping magnet has to drive a variable load, wherein the amount of friction varies with the number of contacts passed over by the switch brushes.

In accordance with this invention, auxiliary magnetic means is associated with the armature of the magnet whereby the-magnet circuit is held closed during practically the entire motive stroke of the armature, and a device is mounted on the magnet structure to open said contacts near the end of the motive stroke so that the magnet may deenergize to permit the armature to restore, the said circuit contacts being held open during practically the entire return movement.

Referring to the drawing which comprises but a single sheet; Fig. 1 is the side elevation of an apparatus constructed in accordance with the invention, the magnet being diagrammatically indicated, the pawl being shown in bolt outline in its normal position and in dotted lines in the position it occupies when the motive stroke is almost complete;v Fig. 2 is an other view showing the relative position of the arm secured to the armature and the magnetic device, which controls the opening and closing of the circuit, at the end of the motive stroke.

The electromagnet (motor magnet) 1 is furnished with a main armature 2 pivoted at 9, which is extended by means of the arm 3 to the pawl 41 which drives the ratchet 5. The larm 3 is provided with an extension piece 6 which is grooved at 7 so as to permit the auxiliary armature 8 pivoted at 9 to move back and forth under the control of the arm 3. The spring 13 is tensioned in a direction tending to maintain the springs 12 and 13 separated. v

In the normal position (Fig. 1) the spring 10 maintains the arm 3 and consequently the extension piece 6 of the arm 3 in a position such thatvtlie lug 20 of the extension piece engages with the auxiliary armature 8. The spring 13 is rigidly secured to the insulating bushing 14 by means of the rivet 21. The bushing is in turn rigidly secured to the auxiliary armature 8 so that the auxiliary armature, bushing and spring 13 move in unison. lith the lug 2O engaging with the auxiliary armature 8 the contact springs l2 and 13 are closed.

yThe principle of operation is as follows:

The closing of key 11 causes the electromagnet 1 to energize and the main armature 2 1s attracted towards the vpole piece 15. The arm 3 and its extension piece 6 are moved in unison and the lug 20 is consequently disengaged from the auxiliary armature 8. When the electromagnet 1 was energlzed, the auxiliary armature 8 was attracted to the pole piece 16 so that it remains in physical contact therewith after the lug 20 has dlsengaged itself from the auxiliary armature 8. The armature 2 continues to move towards the pole piece 15 until the lug 19 engages with the auxiliary armature 8 just before the end of the motive stroke. The arm 3 and the armature 2 continue to move until the lug 19 presses against the auxiliary armature 8 tending to force it away from the pole p lece 16. The lug 19 finally forces the aux1l1ary armature 8 away from the pole piece 16 before the motive stroke of the main armature 2 is completed, and the contact spr1ngs 12 and 13 are consequently separated, openmg the energizing circuit of the electromagnet 1. The arm 3 likewise causes the pawl 4 to be withdrawn from the tooth 17 and places it in a position .to engage with the tooth 18 of thevratchet 5.

The spring 10 which was tensioned by the movement ofthe arm 3 now seeks to retract and in so doing moves the arm 3 so as .to cause the pawl 4 moving in unison therewith to rotate the ratchet 5 one step in a clockwise direction. At the commencement of the return movement of the arm 3, the lug 19 is disengaged from the auxiliary armature 8 but the contact springs 12 and 13 remain open, due to the direction of the tension of the contact spring v13. When the arm 3 again approaches its normal position the lug 20 'engages with the auxiliary armature 8 and as the return movement progresses, the armature is forced against the po-le piece 16, by which time the return movement of the arm 3 is completed. The contact springs 12 and 13 are now closedv completing the energizing circuit of the electromagnet 1 and the cycle of operation is repeated.

It is evldent that by varying the position I of the lugs 19 and 20, the time of opening and more' particularly the time of closing the contact springs 12 and 13 which form part of the energizing circuit of the electromagnet 1 will be advanced or retarded resulting in the close regulation of the operation of the stepping mechanism. What is claimed is:

1. In a stepping mechanism, a motor mag- Y a circuit interrupter controlled by the movel ment of the auxiliary armature, a circuit including the motor magnet and the circuit interrupter, means controlled by the main armature for overcoming the magnetic eii'ect between the motor magnet and the auxiliary armature whereby t-he circuit including the,

motor magnet is opened, and means likewise controlled by the main armature for again closing the circuit of the motor magnet.

3. In a stepping mechanism, a motor magnet, a main armature, an auxiliary armature, a magnetic circuit including said magnet and said auxiliary armature, means whereby said magnetic circuit is opened by the main armature during the latters motive stroke and again closed by it during its driving stroke, a circuit interrupter controlled by the auxiliary armature, and a circuit including the motor magnet and the circuit interrupter.

In witness whereof, I hereunto subscribe my name this 29th day of February, A. D. 1924.

FRANK H. HIBBARD. 

